Field of the Invention
The invention relates to a method for triggering a plurality of relay exciter coils connected parallel to a common voltage source, each of which coils can be turned on and off by relay switching means associated with them, wherein the relay exciter coils to be turned on at a given time, after reaching their response state, are triggered through relay switching means by a common clock generator with a clock ratio in such a way that a steady state of a holding current that is reduced relative to the response state is established. The invention also relates to a circuit for carrying out the method.
A relay is known to have an armature through which switch contacts can be actuated. The force required for the actuation must be brought to bear by the relay exciter coil. A certain current through the exciter coil is necessary in order attract the armature and to the actuate the switch contacts, for a given number of windings on the exciter coil. Since the losses in the magnetic circuit caused by the air gap become less after the attraction of the armature, a lower current than for the attraction suffices to hold the contacts. As a consequence, in general the trigger current of the relay in such a case can be reduced to from one-half to one-third, and as a result the power loss is reduced because of the lower holding current and the attendant warming up of the exciter coil.
Various methods are known to reduce the holding current. One known method includes reducing the holding current, once the response state is reached, by switching over to a voltage source that has a lower supply voltage. Another known method includes triggering the relay, once the response state is reached, with a clock ratio, so that the holding current drops to a steady-state final condition. A further known method is to supply the relay initially with a higher trigger voltage, which can be done with the aid of a voltage multiplier.
If a plurality of relays or relay groups are to be supplied from one voltage source, then a separate circuit is necessary to clock each relay, for example. That entails major expenditure for circuitry and thus high manufacturing costs.